Fluid mixing nozzles for abrasive type slurries and high pressure air have been well known for many years. For example, one such nozzle for use in sand blasting operations is disclosed in U.S. Pat. No. 409,751. In this patent, a stream of sandcarrying water is combined with two air streams directed to mix with the liquid externally with the nozzle to minimize abrasive action on the nozzle itself. In recent years, pollution control devices have been growing in importance and are becoming more and more sophisticated. To reduce air pollution from contaminated stack gases, cooling of the gases initially to reduce the flow volume must be accomplished over very short distances within the stack. Consequently, cooling spray nozzles used for such purposes must be characterized by small liquid droplets having a generally large area and uniform spray pattern. In such applications, the generation of larger size droplets drastically reduces the cooling effectiveness of the nozzles because of the lesser liquid surface and longer residence time of the larger droplets. As a result, maximum evaporation and cooling effects are not achieved.
In more recent times, gas scrubbers have been designed to employ lime slurries. These slurries are most abrasive, and when used in a mixing nozzle which combines the slurries with high velocity air, abrasive wear on the nozzles is extreme. In these nozzles, which treat the gases as well as cool, the high velocity air and lime slurries are generally mixed internally of the nozzle, and in such environments, stainless steel parts may have a useful life of only a few hours, and even tungsten carbide nozzles erode extensively in a matter of about three or four weeks.
The principal object of this invention is to provide an improved mixing nozzle for cooling or treating sprays in which a liquid slurry and high velocity air are combined externally of the nozzle.
Another object of the invention is to provide a nozzle construction of the above type which has improved performance and wear characteristics as compared to presently available nozzles of the same type.
A further object of this invention is to provide a mixing nozzle having a discrete spray forming insert fabricated of an abrasion resistant material .